Compliant connector for land grid array

ABSTRACT

A connector assembly for providing electrical continuity between an array of contacts on an electrical component and a corresponding array of contacts on a printed circuit board. The connector assembly includes a plurality of floating pins. Floatation of the pin within a receptacle of the component body provides a first mode of compliance for electrical components, connector assemblies and printed circuit boards that are not coplanar. For a second mode of compliance to account for non-planarity, each pin includes an elongated, elastically deformable cantilever beam. Each pin is adapted and configured to accommodate the deformed cantilever beam of an adjacent pin without mechanical or electrical contact or interference.

FIELD OF THE INVENTION

[0001] The present invention relates to apparatus and methods forproviding electrical continuity between two objects, and moreparticularly to an array of solderless connectors for use with a landgrid array integrated circuit package.

BACKGROUND OF THE INVENTION

[0002] Land grid array (LGA) connector assemblies are commonly used withintegrated circuit (IC) packages, such as in applications which do notrequire soldering of the pins of the LGA connector assembly to eitherthe IC package or a corresponding circuit board. As one example, an LGAconnector assembly can be used to temporarily place an LGA package inelectrical communication with a circuit card during test, emulation, anddebug procedures. As another example, the LGA socket assembly can beused for upgrades and replacements of LGA packages onto circuit boards.

[0003] The present invention incorporates a variety of novel andunobvious features which are improvements over currently existing LGAsocket assemblies.

SUMMARY OF THE INVENTION

[0004] One aspect of the present invention includes an apparatus forproviding electrical continuity between two objects. The apparatusincludes a body with a top surface and a bottom surface, the bodydefining a plurality of pin receptacles, each receptacle including aguiding slot within the body between the top and bottom surfaces. Theapparatus includes a plurality of pins, each one of the pins beinglocated within a different one of the plurality of receptacles, each pinincluding a centerbody with two edges, a first member extending from thecenterbody, a first cantilever beam extending from the centerbody, and asecond cantilever beam extending from the centerbody. The first memberof each one of the plurality of pins cooperates with the guiding slot ofthe corresponding receptacle to guide the pin within the receptacle,each pin being freely moveable within the corresponding receptacle.

[0005] Another aspect of the present invention includes an apparatus forproviding electrical continuity between two objects. The apparatusincludes a body with a top surface and a bottom surface, the bodydefining a plurality of pin receptacles, each receptacle including anaperture. The apparatus includes a plurality of pins, each one of thepins being loose within a different one of the plurality of receptacles,each pin including a centerbody, a first cantilever beam extending fromof the centerbody at an acute angle relative to the centerbody, and asecond cantilever beam extending from the centerbody at an acute anglerelative to the centerbody. The first cantilever beam includes a freeend that extends over an adjacent one of the pins.

[0006] Another aspect of the present invention includes an apparatus forproviding electrical continuity between two objects. The apparatusincludes a body with a top surface and a bottom surface, the bodydefining a plurality of pin receptacles, each receptacle including anaperture and a guiding slot within the body. The apparatus includes aplurality of pins located within the plurality of receptacles, each pinincluding a planar centerbody, a first member extending from thecenterbody and cooperating with the guiding slot to loosely locate eachpin within a corresponding receptacle, and a first cantilever beamextending from the centerbody. The centerbody includes a projectionextending from a surface of the centerbody, the projection cooperatingwith the receptacle to limit sliding motion of said pin within thereceptacle.

[0007] These and other aspects of the present invention will be apparentfrom the claims, drawings, and the description of the preferredembodiment to follow.

DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a perspective exploded view of an electronic assemblyaccording to one embodiment of the present invention.

[0009]FIG. 2 is a perspective view of the connector assembly of FIG. 1according to one embodiment of the present invention.

[0010]FIG. 3 is a top view of the connector assembly of FIG. 2.

[0011]FIG. 4 is a partial, cross-sectional side elevational view of theconnector assembly of FIG. 3 as taken along line 4-4 of FIG. 3.

[0012]FIG. 5 is a side-elevational view of the connector assembly ofFIG. 4 with the pins removed.

[0013]FIG. 6 is a cross-sectional, front elevational view of theconnector assembly of FIG. 3 as taken along line 6-6 of FIG. 3.

[0014]FIG. 7 is a partial bottom view of the connector body of FIG. 3,with the pins removed.

[0015]FIG. 8 is a top, side, and frontal perspective view of a connectorpin according to one embodiment of the present invention.

[0016]FIG. 9 is a side elevational view of the pin of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] For the purposes of promoting an understanding of the principlesof the invention, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, such alterations andfurther modifications in the illustrated device, and such furtherapplications of the principles of the invention as illustrated thereinbeing contemplated as would normally occur to one skilled in the art towhich the invention relates.

[0018] One embodiment of the present invention includes a connectorassembly for providing electrical continuity between arrays of contactson two objects, such as between an electrical component and a printedcircuit board, or two printed circuit boards or two electricalcomponents. The connector assembly includes a plurality of floatingpins. Floatation of the pin within a receptacle of the component bodyprovides a first mode of compliance or correction for electricalcomponents, connector assemblies, and printed circuit boards that arenot coplanar. For a second mode of compliance or correction to accountfor non-planarity, each pin includes an elongated, elasticallydeformable cantilever beam. Each pin is adapted and configured toaccommodate the deformed cantilever beam of an adjacent pin withoutmechanical or electrical contact or interference.

[0019]FIG. 1 is an exploded, perspective view of an electronic assembly20 according to one embodiment of the present invention. Assembly 20includes a heat sink or cap 25 placed on top of an electronic component30. Electronic component 30 may be of any type, including various landgrid arrays (LGA) containing integrated circuits packaged therein. Thebottom side of electronic component 30 includes a two dimensionalarrangement (in rows and columns) of electrical contact pads 34 that arein electrical communication with the integrated circuits containedwithin component 30. The various signals from the integrated circuitscontained within component 30 are communicated by a land grid arrayconnector assembly 35 to various contacts 49 located on a printedcircuit board 45. An attachment frame 40 includes a central aperture 41in which LGA connector assembly 35 is located. A plurality of fasteners(not shown) cooperating with fastener holes 27, 42, and 47 maintainassembly 20 in a compressed, assembled state. In another embodiment ofthe present invention, connector assembly 35 includes four earsprojecting from each corner of the assembly, each ear including acorresponding fastener hole that aligns with holes 27 and 47. Assembly20 is useful for methods including electrical testing and componentburn-in of component 30. LGA connector assembly 35 provides reliable,temporary electrical communication between LGA component 30 and printingcircuit board 45 in a manner which will be described.

[0020] With reference now FIGS. 2, 3, and 4, a connector assembly 35according to one embodiment of the present invention is shown. Connectorassembly 35 includes a body 100 which defines a plurality of pinreceptacles 105 therein. Preferably, each of the plurality ofreceptacles 105 includes an elastically deformable pin 200 whichprovides electrical continuity from a contact 34 of component 30 to acontact 49 of printed circuit board 45. As best seen in FIG. 3,receptacles 105 are arranged in a plurality of columns in a firstdirection 201, and a plurality of rows in a second direction 202, suchas to form a two dimensional matrix of receptacles 105 and correspondingpins 200.

[0021] In a preferred embodiment, body 100 is molded from anon-conductive material such as Vectra E130i. A preferred embodimentincludes a spacing of 0.050 inches between adjacent columns, and apreferred spacing of 0.050 inches between adjacent rows. In yet anotherembodiment, the preferred spacing between adjacent rows is 1 millimeter,and the spacing between adjacent columns is 1 millimeter. Preferably,the height of body 100 from planar upper surface 110 to planar lowersurface 115 is approximately 1.065 inches.

[0022] Various materials and dimensions are described herein. Thesematerials and dimensions are given as examples, and are intended to benon-limiting examples.

[0023] Referring to FIG. 4, in a preferred embodiment each receptacle105 includes a corresponding pin 200 loosely located therein. Eachreceptacle 105 includes an aperture 106 located therein that extendsfrom top surface 110 to bottom surface 115. The top portion 106 a ofaperture 106 extends along direction 201 for a distance longer than thedistance which bottom portion 106 b of aperture 106 extends along thatsame direction. Thus, as best seen in FIG. 4 and 5, aperture 106 has theappearance of a sideways “L”.

[0024] Referring to FIGS. 5, 6, and 7, each receptacle 105 preferablyincludes a pair of enclosed guiding slots 120 and 125 located alongeither side of receptacle 105 (as best seen in FIG. 6), and abottom-facing surface 130 located between guiding slots 120 and 125.Slot 120 includes a bottom-facing aperture 121 and a top-facing aperture122. Guiding slot 125 includes a bottom-facing aperture 126 and atop-facing aperture 127. Each guiding slot 120 and 125 preferablydefines an internal channel from the bottom-facing aperture to thetop-facing aperture which is preferably square in cross section with adimension of 0.0055 inches×0.0055 inches. A top surface 111 of body 100extends between top-facing apertures 122 and 127.

[0025]FIGS. 8 and 9 show perspective and side elevational views,respectively, of a pin 200 according to one embodiment of the presentinvention. Each pin 200 includes a centerbody 205 having top edges 210 aand 210 b, and bottom edges 215 a and 215 b. Centerbody 205 ispreferably planar and manufactured from sheet material. Each centerbody205 includes front and rear planar surfaces 206 a and 206 b,respectively.

[0026] Each pin 200 includes a first cantilever beam 220 extending fromthe top edge of the centerbody 205 and a second cantilever beam 230extending from the bottom edge of the centerbody 205. First cantileverbeam 220 extends relative to a planar surface of centerbody 205 at anacute angle 221. Second cantilever beam 230 extends relative to a planarsurface of centerbody 205 at an acute angle 231. Preferably, angle 221is greater than about 40 degrees, less than about 75 degrees, and mostpreferably is about 52 degrees. Angle 231 is preferably more than about45 degrees, less than about 80 degrees, and most preferably is about 64degrees.

[0027] Top cantilever beam 220 includes a free end 225 which is adaptedand configured to have an external surface which provides electricalcontinuity with a contact 34 of component 30. Second cantilever beam 230preferably includes a free end 235 adapted and configured to have anoutward surface for providing electrical continuity with a contact 49 ofprinted circuit board 45. In a most preferred embodiment, free end 225is formed to have a radius on the inward surface of about 0.010 inches,and free end 235 is formed to have a radius on the inward surface ofabout 0.0075 inches.

[0028] Top cantilever beam 220 preferably has a width which varies fromapproximately 0.015 as it extends out from centerbody 205, and tapers toabout 0.006 to 0.008 near free end 225. Preferably, second cantileverbeam 230 has a constant width of about 0.013 inches. Preferably, pin 200is fabricated from a material with good spring characteristics and highconductivity, such as #25 BeCu, ½ hard, and age hardened with a tensilestrength between 185 to about 215 KSI. Preferably, the material has athickness of about 0.0042 inches.

[0029] Referring to FIG. 9, first cantilever beam 220 has a length thatis longer than the length of second cantilever beam 230. The furthestmost edge of free end 225 is preferably about 0.055 inches from planarsurface 206 b of centerbody 205. The furthest edge of free end 235 ispreferably about 0.025 inches from planar surface 206 b. Therefore, freeend 225 is horizontally displaced from free end 235 by about 0.03inches. Referring to FIG. 1, this offset results in a similar offset inapparatus 20, such that a corresponding contact pad 34 of component 30is offset horizontally from the corresponding contact 49 of circuitboard 45. Referring to FIG. 4, each pin 200 includes a first cantileverbeam adapted and configured to have a free end 225 that extends over thecenterbody 205 of the adjacent pin.

[0030] Each pin 200 also includes features to guide and limit sliding ofpin 200 within a receptacle 105 of body 100. Each pin 200 includes firstand second members 240 and 245, respectively, extending from edge 210 ofcenterbody 205, and straddling cantilever beam 220. Each member 240 and245 is generally coplanar with centerbody 205, as best seen in FIG. 9.Cantilever beam 220 extends from a central portion of one edge ofcenterbody 205, with first member 240 extending from the edge adjacentto one side of the cantilever beam and second member 245 extending fromthe edge adjacent to the other side of cantilever beam 220.

[0031] Centerbody 205 includes a projection 250 that extends from planarsurface 206 b of centerbody 205, as best seen in FIGS. 8 and 9.Projection 250 extends about 0.0024 inches from planar surface 206 b.

[0032] As seen in FIG. 4, pins 200 are in the free state, with free end225 being above top surface 110, and free end 235 of second cantileverbeam 230 being below bottom surface 115. However, when connectorassembly 35 is used as shown in apparatus 20 of FIG. 1, the bottomsurface of electronic component 30 deflects each first cantilever beam220 downward until the top most surface of free end 225 is at or nearthe plane defined by top surface 110. Likewise, contact with the surfaceof printed circuit board 45 deforms free end 235 of second cantileverbeam 230 so that the exterior surface of free end 235 is at or near aplane defined by bottom surface 115.

[0033] However, contact pressure against second cantilever beam 235,owing to its greater stiffness as compared to first cantilever beam 220,also results in limited upward sliding motion of pin 220 within guidingslots 120 and 125 of receptacle 105. As best seen in FIG. 4, the firstmember 240 extending from centerbody 205 is slidingly received within aguiding slot 120 of the corresponding receptacle. Likewise, the secondmember 245 extending from centerbody 205 is slidingly received withinsecond guiding slot 125. The cooperation of first and second members 240and 245 with guiding slots 120 and 125, respectively, limit slidingmotion of pin 200 within receptacle 105 to a vertical orientation (asseen in FIG. 4). However, the loose sliding motion of pin 200 withinreceptacle 105 is limited. Still referring to FIG. 4, sliding motion inthe downward motion is limited by contact of cantilever beam 220 with asurface 131 of body 100. Upward sliding motion of pin 200 withinreceptacle 105 is limited by contact of projection 250 with surface 130of body 100.

[0034] Owing to the greater stiffness of cantilever beam 230 as comparedto cantilever beam 220, compression of connector assembly 35 between acomponent 30 and printed circuit board 45 results in beam 230 tending topush pin 200 vertically upward. This upward motion is limited by contactof projection 250 with surface 130. In contrast, contact of component 30with the more easily deformable beam 220 tends to result in deformationof beam 220. As previously described, beam 220 is both tapered in widthand also longer than beam 230, such that beam 220 is less resistant tobending than beam 230.

[0035] Referring to FIGS. 1 and 4, compression of a connector assembly35 between a first object such as electrical component 30 and a secondobject such as printed circuit board 45 results in both verticalmovement and deformation of pins 200. Owing to the greater stiffness ofbeam 230, contact of beam 230 with an object results in a first, lesseramount of upward bending and also vertical sliding movement of pin 200within the guiding slots. This sliding movement is limited by contact ofprojection 250 with surface 130. Owing to the lesser stiffness of beam220, contact of beam 220 with an object results in a second greateramount of downward bending. The downward bending movement of free end225 of beam 220 is limited by contact of the inner surface of end 225with top surface 111 of body 100. Further, beam 220 deflects to arecessed position between members 240 and 245 (which are slidinglyreceived within the insulative body material of slots 120 and 125). Thiscombination of contact of free end 225 with surface 111 of a first pin220, the limited upward sliding movement of a second adjacent pin 200,and the deflection of the upper beam of the first pin to a recessedportion of the adjacent second pin prevents the shorting of adjacentpins 200 in apparatus 20. Thus, even though the beam 220 of a first pinoverhangs the centerbody 205 of an adjacent second pin, each pinincludes features that prevent inadvertent electrical contact.

[0036] The long length of upper beam 220 also improves the degree ofcontact between the pin and the electrical contacts of some objects byproviding a wiping action. As an example, as beam 220 is elasticallydeformed downward by mating of assembly 35 and component 30, the freeend 225 of beam 220 also moves laterally with respect to component 30.This lateral motion of free end 225 wipes against the correspondingcontact of component 30, and in some cases mechanically removes anyoxidation layer that has formed on the contact of the object. Thisoxidation layer is noted on board or IC contacts that have been tinplated. Removal of at least some of the oxidation layer reduces thecontact resistance between the component contact and the free end of thepin.

[0037] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same is to be consideredas illustrative and not restrictive in character, it being understoodthat only the preferred embodiment has been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

What is claimed:
 1. An apparatus for providing electrical continuitybetween two objects comprising: a body with a top surface and a bottomsurface, said body defining a plurality of pin receptacles, eachreceptacle including a guiding slot, and; a plurality of pins, each oneof said pins being located within a different one of said plurality ofreceptacles, each pin including a planar centerbody with two edges, afirst member extending from said centerbody and coplanar with saidcenterbody, a first cantilever beam extending from one edge of saidcenterbody at an acute angle relative to said centerbody, and a secondcantilever beam extending from the other edge of said centerbody at anacute angle relative to said centerbody; wherein the first member ofeach one of said plurality of pins cooperates with said guiding slot ofthe corresponding receptacle to guide said pin within said receptacle.2. The apparatus of claim 1 wherein said first cantilever beam is longerthan said second cantilever beam.
 3. The apparatus of claim 1 whereinthe first cantilever beam of a first one of said pins includes a freeend that extends over the centerbody of a second one of said pins. 4.The apparatus of claim 3 wherein said plurality of receptacles arearranged in a matrix of rows and columns.
 5. The apparatus of claim 1wherein each said receptacle includes a second guiding slot, each saidcenterbody includes a second member extending from said centerbody andcoplanar with said centerbody, and each said second member of each oneof said plurality of pins cooperates with said second guiding slot ofthe corresponding receptacle to loosely guide said pin within saidreceptacle.
 6. The apparatus of claim 5 wherein said first cantileverbeam, said first member, and said second member extend from the one edgeof said centerbody, said first cantilever beam extending from thecentral portion of the one edge, said first member extending from theone edge adjacent to one side of said first cantilever beam, said secondmember extending from the one edge adjacent to the other side of saidfirst cantilever beam.
 7. The apparatus of claim 1 wherein each said pinis freely slidable within the corresponding receptacle, and saidcenterbody includes a projection extending from a planar surface of thecenterbody, said projection cooperating with a surface of the receptacleto limit sliding motion of said pin.
 8. An apparatus for providingelectrical continuity between two objects, comprising: a body with a topsurface and a bottom surface, said body defining a plurality of pinreceptacles, and; a plurality of pins, each one of said pins beingloosely located within a different one of said plurality of receptacles,each pin including a centerbody with two edges, a first cantilever beamextending from one edge of said centerbody at an acute angle relative tosaid centerbody, and a second cantilever beam extending from the otheredge of said centerbody at an acute angle relative to said centerbody;wherein the first cantilever beam of each one of said pins includes aflexible free end that extends over said centerbody of an adjacent oneof said pins.
 9. The apparatus of claim 8 wherein said centerbodyincludes projection extending from a planar surface of the centerbody,said projection cooperating with a surface of the receptacle to limitsliding motion of said pin.
 10. The apparatus of claim 8 wherein eachsaid receptacle includes first and second guiding slots, each saidcenterbody includes first and second members extending from saidcenterbody and coplanar with said centerbody, and each said first memberof each one of said plurality of pins is slidably received within saidfirst guiding slot of the corresponding receptacle and each said secondmember of said one of said plurality of pins is slidably received withinsaid second guiding slot of the corresponding receptacle to looselyguide said pin within said receptacle.
 11. The apparatus of claim 10wherein said first cantilever beam, said first member, and said secondmember extend from the one edge of said centerbody, said firstcantilever beam extending from the central portion of the one edge, saidfirst member extending from the one edge adjacent to one side of saidfirst cantilever beam, said second member extending from the one edgeadjacent to the other side of said first cantilever beam.
 12. Theapparatus of claim 8 wherein said centerbody includes a planar surface,said second cantilever beam has a free end, and the length from theplanar surface to the free end of said first cantilever beam is greaterthan the length from the planar surface to the free end of said secondcantilever beam.
 13. The apparatus of claim 12 wherein each receptacleincludes an aperture extending from the top surface to the bottomsurface.
 14. An apparatus for providing electrical continuity betweentwo objects comprising: a body with top a surface and a bottom surface,said body defining a plurality of pin receptacles, each receptacleincluding a guiding slot within the body between the top and bottomsurfaces, and; a plurality of pins, each one of said pins being locatedwithin a different one of said plurality of receptacles, each pinincluding a planar centerbody with a first edge, a first memberextending from said centerbody and cooperating with the guiding slot toloosely locate each said pin within a corresponding said receptacle, anda first cantilever beam extending from the first edge of said centerbodyat an acute angle relative to said centerbody; wherein said centerbodyincludes a projection extending from a planar surface of the centerbody,said projection cooperating with a surface of the receptacle to limitsliding motion of said pin within the receptacle.
 15. The apparatus ofclaim 14 wherein the first cantilever beam of a plurality of said pinsincludes a free end that extends over the centerbody of an adjacent oneof said pins.
 16. The apparatus of claim 14 wherein said plurality ofreceptacles are arranged in a matrix of rows and columns.
 17. Theapparatus of claim 14 wherein each said receptacle includes a secondguiding slot, each said centerbody includes a second member extendingfrom said centerbody, and each said second member of each one of saidplurality of pins cooperates with said second guiding slot of thecorresponding receptacle to loosely guide said pin within saidreceptacle.
 18. The apparatus of claim 17 wherein said first cantileverbeam, said first member, and said second member extend from the one edgeof said centerbody, said first cantilever beam extending from thecentral portion of the one edge, said first member extending from theone edge adjacent to one side of said first cantilever beam, said secondmember extending from the one edge adjacent to the other side of saidfirst cantilever beam.
 19. The apparatus of claim 14 wherein saidcenterbody includes a second edge opposite the first edge, and whichfurther comprises a second cantilever beam extending from the secondedge, wherein said first cantilever beam is longer than said secondcantilever beam.
 20. The apparatus of claim 14 wherein said firstcantilever beam has a free state in which a free end of said cantileverbeam extends beyond the top surface of said body, a compressed state inwhich said free end is elastically deformed to be in the plane of thetop surface, and in the compressed state the free end of said pinextends over the centerbody of an adjacent one of said pins.
 21. Amethod for establishing electrical continuity in a solderless connectionbetween two object, comprising: providing a first object with a firstplurality of electrical contacts, a second object with an plurality ofelectrical contacts, and a connector assembly including a body with anupper surface and a lower surface and a plurality of electricallyconductive pins, each pin being loosely retained within the body, eachpin including a bendable upper member and a bendable lower member;pressing the first object against the plurality of bendable lowermember; pressing the second object against the plurality of bendableupper members; and sliding of the plurality of pins toward the secondobject by said pressing the first object.
 22. The method of claim 21which further comprises: elastically deforming the plurality of lowermembers by a first amount by said pressing the first object; andelastically deforming the plurality of upper members by a second amountby said pressing the second object, the second amount being greater thanthe first amount.
 23. The method of claim 21 which further compriseselastically deforming the plurality of upper members by said pressingthe second object, wherein at least some of the deformed upper membershave a portion which is spaced above a portion of an adjacent pin.